scholarly journals Mechanism of magnesium transport in spinel chalcogenides

2021 ◽  
Author(s):  
Mohsen Sotoudeh ◽  
Manuel Dillenz ◽  
Axel Groß
Keyword(s):  
Ionic Conductivity ◽  
Ion Mobility ◽  
Density Functional ◽  
Electrode Materials ◽  
Critical Role ◽  
High Energy ◽  
Ion Concentration ◽  
Critical Parameters ◽  
Site Preference ◽  
The Impact

Abstract In the area of sustainable energy storage, batteries based on multivalent ions such as magnesium have been attracting considerable attention due to their potential for high energy densities. Furthermore, they are typically also more abundant than, e.g., lithium. However, as a challenge their low ion mobility in electrode materials remains. This study addresses the ionic conductivity of magnesium in spinel host materials based on periodic density functional theory calculations in order to identify the critical parameters which determine the mobility and insertion of ions. We will in particular highlight the critical role that trigonal distortions of the spinel structure play for the ion mobility. In detail, we will show that it is the competition between coordination and bond length that governs the Mg site preference in ternary spinel compounds upon trigonal distortions which can only be understood by also taking covalent interactions into account. Based on our theoretical study, we rationalize the impact of the metal distribution in the host material and the ion concentration on the diffusion process. Furthermore, cathode-related challenges for practical devices will be addressed. Our findings shed light on the fundamentional mechanisms underlying ionic conductivity in solid hosts and thus may contribute to improve ion transport in battery electrodes.

scholarly journals Mechanism of magnesium transport in spinel chalcogenides

2021 ◽  
Author(s):  
Mohsen Sotoudeh ◽  
Manuel Dillenz ◽  
Axel Groß
Keyword(s):  
Ionic Conductivity ◽  
Ion Mobility ◽  
Density Functional ◽  
Electrode Materials ◽  
Critical Role ◽  
High Energy ◽  
Ion Concentration ◽  
Critical Parameters ◽  
Site Preference ◽  
The Impact

Abstract In the area of sustainable energy storage, batteries based on multivalent ions such as magnesium have been attracting considerable attention due to their potential for high energy densities. Furthermore, they are typically also more abundant than, e.g., lithium. However, as a challenge their low ion mobility in electrode materials remains. This study addresses the ionic conductivity in spinel host materials which represent a promising class of cathode and solid-electrolyte materials in Mg-ion batteries. Based on periodic density functional theory calculations, we identify the critical parameters which determine the mobility and insertion of ions. We will in particular highlight the critical role that trigonal distortions of the spinel structure play for the ion mobility. In detail, we will show that it is the competition between coordination and bond length that governs the Mg site preference in ternary spinel compounds upon trigonal distortions. This can only be understood by also taking covalent interactions into account. Furthermore, our calculations suggest that anionic redox plays a much more important role in sulfide and selenide spinels than in oxide spinels. Based on our theoretical study, we rationalize the impact of the metal distribution in the host material and the ion concentration on the diffusion process. Furthermore, cathode-related challenges for practical devices will be addressed. Our findings shed light on the fundamentional mechanisms underlying ionic conductivity in solid hosts and thus may contribute to improve ion transport in battery electrodes.

scholarly journals In-Silico Prediction of Annihilators for Triplet Fusion Upconversion via Auxiliary-Field Quantum Monte Carlo

2020 ◽  
Author(s):  
John Weber ◽  
Emily Churchill ◽  
Evan J. Arthur ◽  
Andrew Pun ◽  
Shiwei Zhang ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Electronic Structure ◽  
Quantum Monte Carlo ◽  
In Silico ◽  
Density Functional ◽  
Energy Gap ◽  
Critical Role ◽  
High Energy ◽  
Auxiliary Field ◽  
Hybrid Functional

<div>The energy of the lowest-lying triplet state (T1) relative to the ground and first-excited singlet states (S0, S1) plays a critical role in optical multiexcitonic processes of organic chromophores. Focusing on triplet fusion upconversion, the S0 to T1 energy gap, known as the triplet energy, is difficult to measure experimentally for most molecules of interest. Ab initio predictions can provide a useful alternative, however</div><div>low-scaling electronic structure methods such as the Kohn-Sham and time-dependent variants of Density Functional Theory (DFT) rely heavily on the fraction of exact exchange chosen for a given functional, and tend to be unreliable when strong electronic correlation is present. Here, we apply auxiliary-field quantum Monte Carlo (AFQMC), a scalable electronic structure method capable of accurately describing even strongly correlated molecules, to predict the triplet energies for a series of candidate annihilators for triplet fusion (TF) upconversion, including 9,10 substituted anthracenes and substituted benzothiadiazole (BTD) and benzoselenodiazole (BSeD) compounds. We compare our results to predictions from a number of commonly used DFT functionals, as well as DLPNO-CCSD(T0), a localized approximation to coupled cluster with singles, doubles, and perturbative triples. Together with S1 estimates from absorption/emission spectra, which are well-reproduced by TD-DFT calculations employing the range-corrected hybrid functional CAM-B3LYP, we provide predictions regarding</div><div>the thermodynamic feasibility of upconversion by requiring a) the measured T1 of the sensitizer exceeds that of the calculated T1 of the candidate annihilator, and b) twice</div><div>the T1 of the annihilator exceeds its S1 energetic value. We demonstrate a successful example of in silico discovery of a novel annihilator, phenyl-substituted BTD, and present experimental validation of upconverted blue light emission when coupled to a platinum octaethylporphyrin (PtOEP) sensitizer. The BTD framework thus represents a new class of annihilators for TF upconversion. Its chemical functionalization, guided by the computational tools utilized herein, provides a promising route towards high energy (violet to near-UV) emission.</div>

scholarly journals Some Trinitroazetidine Isomers - A DFT Treatment

2021 ◽  
pp. 85-98
Author(s):  
Lemi Türker
Keyword(s):  
Density Functional Theory ◽  
Quantum Chemical ◽  
Spectral Properties ◽  
Density Functional ◽  
High Energy ◽  
Explosive Material ◽  
Functional Theory ◽  
The Impact

The present study considers some trinitroazetidine isomers within the realm of density functional theory (B3LYP/6-311++G(d,p)). One of the isomers considered is 1,3,3-trinitroazetidine (TNAZ) which is the well known insensitive high energy explosive material. Various structural, energetic, quantum chemical and spectral properties of the isomers have been harvested and discussed. Some of the isomers have nitramine bonds and some possess only C-NO2 bonds. The results indicate that the nitramine moiety somewhat destabilizes the structure electronically but increases the impact insensitivity.

scholarly journals Identification of Restricting Parameters on Steps toward the Intermediate-Temperature Planar Solid Oxide Fuel Cell

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6404
Author(s):  
Yongqing Wang ◽  
Bo An ◽  
Ke Wang ◽  
Yan Cao ◽  
Fan Gao
Keyword(s):  
Activation Energy ◽  
Ionic Conductivity ◽  
Electrode Materials ◽  
Development Trend ◽  
Internal Resistance ◽  
Intermediate Temperature ◽  
Critical Parameters ◽  
Critical Ratio ◽  
Operational Temperature ◽  
Intermediate Electrode

To identify critical parameters upon variable operational temperatures in a planar SOFC, an experimentally agreeable model was established. The significance of temperature effect on the performance of SOFC components was investigated, and the effect of activation energy during the development of intermediate electrode materials was evaluated. It is found the ionic conductivity of electrolytes is identified to be unavoidably concerned in the development of the intermediate-temperature SOFC. The drop of the ionic conductivity of the electrolyte decreases the overall current density 63% and 80% at temperatures reducing to 700 °C and 650 °C from 800 °C. However, there exists a critical value on the defined ratio between the electric resistance of the electrolyte in the overall internal resistance of SOFC, above which the further increase in the ionic conductivity would not significantly improve the performance. The lower the operational temperature, the higher critical ratio of the electrical resistance in the overall internal resistance of the cell. The minimal decrease in the activation energy during the development of intermediate electrode materials can significantly enhance the overall performance. Considering the development trend toward the intermediate temperature SOFC, advanced electrode material with the decreased activation energy should be primarily focused. The result provides a guidance reference for developing SOFC with the operational temperature toward the intermediate temperature.

Computational Study of the Decomposition of Cyclotetramethylenetetranitramine under Impact, Friction, and Electric Fields

2015 ◽  
Vol 1096 ◽  
pp. 407-412
Author(s):  
Hui Hu ◽  
Miao Miao Li ◽  
Bao Shan Wang
Keyword(s):  
Electric Fields ◽  
Energetic Materials ◽  
Density Functional ◽  
Computational Study ◽  
Minimum Energy ◽  
High Energy ◽  
High Energy Density ◽  
Basis Sets ◽  
Gas Phases ◽  
The Impact

Organic CHNO-containing high energy density materials have been widely used for storing large amounts of the chemical energies which can be rapidly transformed into heat upon various external perturbations during detonation. The sensitivity of the energetic materials is subjected to considerable concern for safety and maintenance. Periodic density functional theory with the all-electron basis sets were employed in this work to unravel the impact, friction, and electric-fields induced decomposition of HMX. The minimum energy paths for the N−NO2homolysis reactions of HMX in the bulk and gas phases were obtained. The surface-enhanced effect on the decomposition of HMX were calculated for both (010) and (100) surfaces. A general theoretical scheme has been proposed to assess the intrinsic mechanic and electrostatic sensitivities of the pure energetic materials.

scholarly journals Synthesis and Electrochemical Properties of Bi2MoO6/Carbon Anode for Lithium-Ion Battery Application

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1132 ◽  
Author(s):  
Tingting Zhang ◽  
Emilia Olsson ◽  
Mohammadmehdi Choolaei ◽  
Vlad Stolojan ◽  
Chuanqi Feng ◽  
...  
Keyword(s):  
Density Functional ◽  
Electrode Materials ◽  
Electronic Conductivity ◽  
Lithium Ion ◽  
Reversible Capacity ◽  
High Energy ◽  
Carbon Composite ◽  
High Energy Density ◽  
Carbon Anode ◽  
Li Ion

High capacity electrode materials are the key for high energy density Li-ion batteries (LIB) to meet the requirement of the increased driving range of electric vehicles. Here we report the synthesis of a novel anode material, Bi2MoO6/palm-carbon composite, via a simple hydrothermal method. The composite shows higher reversible capacity and better cycling performance, compared to pure Bi2MoO6. In 0–3 V, a potential window of 100 mA/g current density, the LIB cells based on Bi2MoO6/palm-carbon composite show retention reversible capacity of 664 mAh·g−1 after 200 cycles. Electrochemical testing and ab initio density functional theory calculations are used to study the fundamental mechanism of Li ion incorporation into the materials. These studies confirm that Li ions incorporate into Bi2MoO6 via insertion to the interstitial sites in the MoO6-layer, and the presence of palm-carbon improves the electronic conductivity, and thus enhanced the performance of the composite materials.

scholarly journals Solvent-Free Mechanochemical Approach towards Thiospinel MgCr2S4 as a Potential Electrode for Post-Lithium Ion Batteries

Batteries ◽  
2020 ◽  
Vol 6 (3) ◽  
pp. 43
Author(s):  
Laura Caggiu ◽  
Stefano Enzo ◽  
Lorenzo Stievano ◽  
Romain Berthelot ◽  
Claudio Gerbaldi ◽  
...  
Keyword(s):  
Ion Mobility ◽  
Lithium Batteries ◽  
Density Functional ◽  
Lithium Battery ◽  
Electrode Materials ◽  
Lithium Ion ◽  
Functional Theory ◽  
Potential Electrode ◽  
New Compounds ◽  
Induced Reaction

Several new compounds, with desirable properties of ion mobility and working voltage, have been recently proposed using a density functional theory (DFT) computational approach as potential electrode materials for beyond-lithium battery systems. After evaluation of the ‘energy above hull’, thiospinel MgCr2S4 has been suggested as interesting multivalent battery cathode candidate, even though the synthesis of its exact stoichiometry poses serious challenges. In this work, MgCr2S4 is prepared using an innovative mechanochemical route starting from magnesium or magnesium hydride, chromium, and sulfur powders. The progress of such mechanically induced reaction as a function of processing time is carefully monitored by XRD with Rietveld refinement, evidencing the occurrence of a mechanically induced self-propagating reaction (MSR). The effect of parameters associated with the milling apparatus (impact energy) on the products composition are also investigated. To our knowledge, this work represents the first report of the scalable and simple mechanical alloying synthesis of thiospinel MgCr2S4 (space group Fd-3 m, a = 10.09 Å) and opens up interesting possibilities for the exploitation of such material in next-generation post-lithium batteries.

scholarly journals Design and Selection of Pyrazolo[3,4-d][1,2,3] Triazole-based High-energy Materials

2021 ◽  
Author(s):  
Xinghui Jin ◽  
Luhao Liu ◽  
Jianhua Zhou ◽  
Bingcheng Hu
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
High Energy ◽  
Impact Sensitivity ◽  
High Energy Density ◽  
Heats Of Formation ◽  
Detonation Properties ◽  
Detonation Pressure ◽  
The Impact ◽  
Impact Sensitivities

Abstract In this study, we design a series of bridged energetic compounds based on pyrazolo[3,4-d][1, 2, 3]triazole to screen potential energetic materials with excellent detonation properties and acceptable sensitivities. The electronic structures, heats of formation, detonation velocity, detonation pressure, and impact sensitivity of the designed compounds were calculated using density functional theory. The results showed that the designed compounds have high positive heats of formation in the range of 1035.4 (A7) to 2851.4 kJ mol−1 (D2). Moreover, the designed compounds have high crystal densities and heats of detonation, which significantly enhance detonation pressures and velocities. The detonation pressures and velocities are in the ranges of 6.23 (A1) to 9.65 km s−1 (D3) and 15.7 to 43.9 GPa (E8), respectively. The impact sensitivity data also suggest that the designed compounds have impact sensitivities in an acceptable range. Considering detonation pressures, detonation velocities, and impact sensitivities, six compounds (C3, C5, D3, D5, E3, and F3) were screened as potential materials with high energy density, excellent detonation properties, and low impact sensitivities. Finally, the electronic structures of the screened compounds were simulated to provide further understanding on the physicochemical properties of these compounds.

scholarly journals Efficient Stabilization of Na Storage Reversibility by Ti Integration into O′3-Type NaMnO2

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Takuro Sato ◽  
Kazuki Yoshikawa ◽  
Wenwen Zhao ◽  
Tokio Kobayashi ◽  
Hongahally Basappa Rajendra ◽  
...  
Keyword(s):  
Binary System ◽  
Electrode Materials ◽  
Storage System ◽  
Energy Storage System ◽  
Rietveld Analysis ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrode Performance ◽  
The Impact

The development of an energy storage system with abundant elements is a key challenge for a sustainable society, and the interest of Na intercalation chemistry is extending throughout the research community. Herein, the impact of Ti integration into NaMnO2 in a binary system of x NaMnO2–(1–x) TiO2 (0.5≤x≤1) is systematically examined for rechargeable Na battery applications. Stoichiometric NaMnO2, which is classified as an in-plane distorted O′3-type layered structure, delivers a large initial discharge capacity of approximately 200 mAh g-1, but insufficient capacity retention is observed, most probably associated with dissolution of Mn ions on electrochemical cycles. Ti-substituted samples show highly improved electrode performance as electrode materials. However, the appearance of a sodium-deficient phase, Na4Mn4Ti5O18 with a tunnel-type structure, is observed for Ti-rich phases. Among the samples in this binary system, Na0.8Mn0.8Ti0.2O2 (x=0.8), which is a mixture of a partially Ti-substituted O′3-type layered oxide (Na0.88Mn0.88Ti0.12O2) and tunnel-type Na4Mn4Ti5O18 as a minor phase elucidated by Rietveld analysis on both neutron and X-ray diffraction patterns, shows good electrode performance on the basis of energy density and cyclability. Both phases are electrochemically active as evidenced by in situ X-ray diffraction study, and the improvement of reversibility originates from the suppression of Mn dissolution on electrochemical cycles. From these results, the feasibility of Mn-based electrode materials for high-energy rechargeable Na batteries made from only abundant elements is discussed in detail.

Physicochemical Properties of Alkaline Aqueous Sodium Metaborate Solutions

2006 ◽  
Vol 4 (1) ◽  
pp. 88-98 ◽  
Author(s):  
Caroline R. Cloutier ◽  
Akram Alfantazi ◽  
Elod Gyenge
Keyword(s):  
Ionic Conductivity ◽  
Physicochemical Properties ◽  
Aqueous Solutions ◽  
Aqueous Media ◽  
Ion Concentration ◽  
X Ray Diffraction ◽  
Sodium Metaborate ◽  
Commercial Viability ◽  
The Impact ◽  
And Storage

Background: The transition to a hydrogen fuel economy is hindered by the lack of a practical storage method and concerns associated with its safe handling. Chemical hydrides have the potential to address these concerns. Sodium borohydride (sodium tetrahydroborate, NaBH4), is the most attractive chemical hydride for H2 generation and storage in automotive fuel cell applications, but recycling from sodium metaborate (NaBO2), is difficult and costly. An electrochemical regeneration process could represent an economically feasible and environmentally friendly solution. Method of Approach: We report a study of the properties of concentrated NaBO2 alkaline aqueous solutions that are necessary to the development of electrochemical recycling methods. The solubility, pH, density, conductivity, and viscosity of aqueous NaBO2 solutions containing varying weight percentages (1, 2, 3, 5, 7.5, and 10wt.%) of alkali hydroxides (NaOH, KOH, and LiOH) were evaluated at 25°C. The precipitates formed in supersaturated solutions were characterized by x-ray diffraction and scanning electron microscopy. Results: All NaBO2 physicochemical properties investigated, except solubility, increased with increased hydroxide ion concentration. The solubility of NaBO2 was enhanced by the addition of KOH to the saturated solution, but decreased when LiOH and NaOH were used. The highest ionic conductivity (198.27S∕m) was obtained from the filtrate of saturated aqueous solutions containing more than 30wt.%NaBO2 and 10wt.% NaOH prior to filtration. At 10wt.% hydroxide, the viscosity of the NaBO2 solution was the highest in the case of LiOH (11.38 cP) and lowest for those containing NaOH (6.37 cP). The precipitate was hydrated, NaBO2 for all hydroxides, but its hydration level was unclear. Conclusions: The use of KOH as the electrolyte was found to be more advantageous for the H2 storage and generation system based on NaBO2 solubility and solution half-life. However, the addition of NaOH led to the highest ionic conductivity, and its use seems more suitable for the electroreduction of NaBO2. Further investigations on the impact of KOH and NaOH on the electroreduction of NaBO2 in aqueous media have the potential to enhance the commercial viability of NaBH4.

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